The present invention relates to an electromagnetic actuator for the actuation of the valves of an internal combustion engine.
As is known, internal combustion engines are currently being tested in which the intake and exhaust valves that selectively bring the combustion chamber of the engine into communication with the intake manifold and the exhaust manifold respectively of the engine are actuated by electromagnetic actuators driven by an electronic control unit. This solution makes it possible to vary, in a very precise manner, the lift, opening time, and opening and closing moments of the valves as a function of the angular speed of the crankshaft and of other operating parameters of the engine, substantially increasing the performance of the engine.
The electromagnetic actuator that currently provides the best performance is disposed alongside the stem of the valve of the internal combustion engine to be axially moved and comprises a support frame secured to the head of the internal combustion engine, an oscillating arm of ferromagnetic material having a first end hinged on the support frame in order to be able to oscillate about an axis of rotation perpendicular to the longitudinal axis of the valve, and a second end shaped as a curved finger disposed in abutment on the upper end of the stem of the valve, and a pair of electromagnets disposed on opposite sides of the central portion of the oscillating arm in order to be able to attract, on command and alternatively, the oscillating arm by causing it to rotate about its axis of rotation.
The electromagnetic actuator lastly comprises two elastic members, the first of which is adapted to maintain the valve of the engine in a closed position and the second of which is adapted to maintain the oscillating arm in a position such as to maintain this valve in the position of maximum opening. The two elastic members act in opposition against one another and are dimensioned such as to position, when neither of the electromagnets is being supplied, i.e. they are in a condition of equilibrium, the oscillating arm in a rest position in which it is substantially equidistant from the polar heads of the two electromagnets so as to maintain the valve of the engine in an intermediate position between the closed position and the position of maximum opening.
The main drawback of the electromagnetic actuator described above is that its electricity consumption is still too high to enable it to be mounted on the internal combustion engines that are normally installed in automobile vehicles. In order to provide for such a large energy requirement it would in practice be necessary to provide the internal combustion engines currently in use with high-power electrical generators of an unacceptably large size.
The object of the present invention is to provide an electromagnetic actuator for the actuation of the valves of an internal combustion engine that has a lower electricity consumption than current actuators.
The present invention therefore relates to an electromagnetic actuator for the actuation of the valves of an internal combustion engine that comprises a head and at least one intake and/or exhaust valve which may move axially in the head between a closed position and a position of maximum opening, the electromagnetic actuator being adapted to move this valve, on command, between its closed position and its position of maximum opening, the electromagnetic actuator comprising an oscillating arm having a first end hinged on a fixed support and a second end in abutment on the valve, and a pair of electromagnets disposed on opposite sides of the oscillating arm and adapted to move the oscillating arm, on command, in order axially to displace the valve between the closed position and the position of maximum opening, the electromagnetic actuator being characterised in that the portion of the oscillating arm that faces the electromagnets comprises a pack of sheets of ferromagnetic material.